Efficient PbS Quantum Dot Solar Cells with Both Mg-Doped ZnO Window Layer and ZnO Nanocrystal Interface Passivation Layer.

Hao Ren,Lintao Hou,Donghuan Qin,Ao Xu,Dan Wang,Yiyang Pan

doi:10.3390/nano11010219

Hao Ren, Lintao Hou + Show 4 more

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https://doi.org/10.3390/nano11010219

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Abstract

In this paper, a Mg-doped ZnO (MZO) thin film is prepared by a simple solution process under ambient conditions and is used as the window layer for PbS solar cells due to a wide n-type bandgap. Moreover, a thin layer of ZnO nanocrystals (NCs) was deposited on the MZO to reduce carrier recombination at the interface for inverted PbS quantum dot solar cells with the configuration Indium Tin Oxides (ITO)/MZO/ZnO NC (w/o)/PbS/Au. The effect of film thickness and annealing temperature of MZO and ZnO NC on the performance of PbS quantum dot solar cells was investigated in detail. It was found that without the ZnO NC thin layer, the highest power conversion efficiency(PCE) of 5.52% was obtained in the case of a device with an MZO thickness of 50 nm. When a thin layer of ZnO NC was introduced between MZO and PbS quantum dot film, the PCE of the champion device was greatly improved to 7.06% due to the decreased interface recombination. The usage of the MZO buffer layer along with the ZnO NC interface passivation technique is expected to further improve the performance of quantum dot solar cells.

Highlights

PbS colloidal quantum dot (CQD) solar cells have been rapidly developed in recent years with a certified power conversion efficiency (PCE) up to 13% in an optimal device configuration [1,2]
A thin layer of zinc oxide (ZnO) NC film was obtained by spin-coating the ZnO NC solution on the Indium Tin Oxides (ITO)/Mg-doped ZnO (MZO) substrate at 3000 rpm for 20 s
The ITO/MZO/ZnO NC samples were annealed at 100 ◦ C for 5 min to eliminate any organic solvents

Summary

Introduction

PbS colloidal quantum dot (CQD) solar cells have been rapidly developed in recent years with a certified power conversion efficiency (PCE) up to 13% in an optimal device configuration [1,2]. The significant performance improvement of PbS CQD solar cells is mainly attributed to the developing ligand exchange technique, interface engineering, and optimized device architecture. It is well known that PbS CQDs are usually capped by insulating ligands, such as oleic acid and oleic amine, during the synthesis processes. These insulating ligands will later become defects and carrier traps in the photovoltaic devices, which are mainly responsible for the low device performance [14,15].

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